My previous method using the PIC involved setting the output to 10.000MHz connected to a relatively accurate frequency counter for monitoring purposes.
Then I ramped the oven temp up to about 40C for a place to start. The outter shield wasn't soldered yet and I had the thermistor taped to the outside of the oven above the crystal.
This was wrapped in foam for insulation in order to stabilize my readings.
I had a current meter in series to monitor the oven's state.
I tracked the freq shift down til it leveled out and my temp was showing abit under 45C.
I waited for everything to stabilize which took 20 min or so.
My PIC code has a calibrate function so I entered in the offset to make my counter show 10.000MHz.
Then I played with that while using a receiver to zero beat WWV, calibrating both the PIC and the counter in the process (for the moment, it's a $100 counter :)
I didn't notice the wayward drifting til I started using it in the U3S and racking up some hours.
I hope this clarifies things.